Lamp (electrical component)
The light bulb is one of the most significant inventions in the history of the human race, illuminating the darkness of the evening and bringing light indoors at all times in order focus on the task at hand. Creating the technology to build and mass produce light bulbs also kindled the development of science during the industrial revolution.
Originally, artificial light was generated by an open flame – in a rustic torch burning in a wall bracket, a hand-held candle or lantern, and later with natural gas lighting. Electricity was first used to produce light with the arc lamp, demonstrated in the early 19th Century. Competition from skilled businessman and inventor Thomas Edison brought his improved incandescent light bulb to prominence in the marketplace during the middle of the century, dominating over other lighting technologies. For more information about the "first" light bulb, refer to the history of the incandescent lamp.
"Lamp" is the technical word for a light bulb, which features an airtight glass enclosure in a "bulb" shape (or a fluorescent "tube") surrounding a thin metal filament. These components are mounted in a ceramic or metal base, which makes an electrical connection in the socket of a light fixture with a threaded base, with two metal pins or a "bayonet mount" (candelabra base). "Re-lamping" refers to the replacement of only the removable lamp in a light fixture.
- Lamp is also a general word for any device that produces artificial light, such as a desk lamp or reading lamp. For other meanings, see Lamp.
Incandescent lamp
The incandescent light bulb was the first type of modern electric light, introduced in the early 19th Century and still basically inefficient at converting electricity to light. About 90% of the electricity input is wasted as heat. This excess heat is then dumped into the air which, in warm climates, must then be cooled by ventilation or air conditioning, resulting in more energy wastage.
Halogen lamps were introduced as an improvement to incandescents. Visible light output of these lamps is about 15% of the energy input, instead of 10%, allowing them to produce a total of about 50% more light using the same amount of electrical power. The bulb capsule is under high pressure instead of a vacuum or low-pressure noble gas. Good halogen bulbs produce a "cool white" color temperature approaching the appearance of sunlight at noon, while regular incandescents produce warm light with a warm yellow tint.
These lamps are much smaller that incandescent and burn with a hotter filament temperature, which results in a very hot surface. For this reason, a fused-quartz "capsule" is used to enclose the filament, which is sealed behind an additional layer of glass. This is a safety precaution, because halogen "bulbs" can explode if broken while operating or by coming into contact with water or oily residue from fingerprints. The risk of burns or fire is also greater than other bulbs, leading to their prohibition in some places.
Fluorescent lamp
Fluorescent lamps have an efficiency of about 40%, meaning that for the same amount of light generated, they use 1/4 the power and produce 1/6 the heat of a regular incandescent. Fluorescents were limited to linear and a round "circleline" lamp until the 1980s, when the compact fluorescent lamp (CFL) was invented. CFLs can have a built-in electrical ballast which fit into a standard screw base, or make use of a remote ballast. Compact and linear fluorescent lamps last far longer than incandescents, but do have some starting trouble in very cold weather when installed outside.
Fluorescents most often come in cool white (CW), with some home bulbs being a warm white (WW), which has a pinkish tint. In between there is an "enhanced white" (EW), which is more neutral. There is also a very cold daylight white (DW). Compact fluorescent lamps are usually considered warm white, though many have a yellowish cast like an incandescent. "Warm" and "cool" are entirely relative terms and almost arbitrary so color temperature and the color rendering index (CRI) are used as absolute scales of color for fluorescents, and sometimes for other types of lighting.
HID lamp
High-intensity discharge lighting first came about with the mercury-vapor streetlights, and later the high-pressure sodium ones with their characteristic orange color. Modern ones are metal halide, used in everything from headlights to floodlights, and with a more pleasant color balance. Like fluorescents, all HID bulbs require a ballast, but they also require a few minutes (or seconds for headlights) to warm up after "igniting". HID bulbs are over 60% and up to 80% efficient.
LED lamp
University researchers have made recent advances in the production of white Light Emitting Diodes LEDs which lead to the introduction of Solid State Lighting (SSL) fixtures made for general illumination. Before this time, colored LEDs were used as indicator lights for electronic devices. These lamps are still more expensive than other lamps, but they last an extremely long time, up to 100,000 hours (compared to around 10,000 for fluorescent and 1,000 for incandescent). It appears that for now these will be most useful and cost-effective in smaller applications, starting with nightlights and flashlights. Colored LEDs can also be used for accent lighting, and even in fake ice cubes for drinks at parties. They are also being increasingly used as Christmas lights. White LEDs are about the same efficiency as other fluorescents, while red ones can be up to 90% efficient.
LED technology is useful for lighting designers because of its low power consumption, low heat generation, instantaneous on/off control, continuity of color throughout the life of the diode and relatively low cost of manufacture. In the last few years, software has been developed to merge lighting and video by enabling lighting designers to stream video content to their LED fixtures, creating low resolution video walls.
Arc lamp
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